Conventional AC coupling circuits (i.e., ACC) are used in hard disc drive (i.e., HDD) read channels. An ACC circuit provides adjustable attenuation ranging from several dBs to about twenty dBs. An ACC circuit also provides a high dynamic high pass filter time constant that ranges from several hundred pico-seconds to several micro-seconds. An ACC circuit should have a reasonable input bandwidth in various different working modes. Switches used in capacitor branches of a conventional ACC circuit will have an influence on the ACC performance, especially when the resistance of switches is comparable to a resistor used in the high pass filter when a short high pass filter time constant is being designed. The switches also contribute parasitic capacitances at an input node of the ACC circuit.
It would be desirable to implement an AC coupling circuit integrated with hybrid switches.